Synthesis of helically twisted [1 + 1]macrocycles assisted by amidinium-carboxylate salt bridges and control of their chiroptical properties

A series of optically active, helically twisted [1 + 1]macrocycles connected via o-, m-, and p-linkages (o-, m-, and p-) was prepared from the corresponding linear duplexes stabilized by complementary amidinium-carboxylate salt bridges bearing two arms with terminal vinyl groups at both ends through the ring-closing metathesis reaction in the good yields of 67, 92, and 96%, respectively. The chiroptical properties of the macrocycles were dependent on the linker geometries and could be controlled by acid-base interactions and zinc coordination, the changes in which were detected by their CD and absorption spectral changes and fluorescence colors.